Patients between 18 and 65 years of age with HIV infection who have stable HIV levels at less than 30,000 copies/mL of blood and CD4 T cell counts higher than 400 cells/cmm may be eligible for this study. Patients who have taken drugs that affect the immune system, such as IL-2 and interferon, in the past 5 years may not participate. Candidates are screened with a comprehensive medical examination, including physical examination and laboratory studies. X-rays, consultations, and biopsies are done only if medically indicated.